AU2009200205B2

AU2009200205B2 - Fuel supply arrangement for a gas turbine

Info

Publication number: AU2009200205B2
Application number: AU2009200205A
Authority: AU
Inventors: Damir Cankovic; Albert Keller; Oliver Konradt
Original assignee: Alstom Technology AG
Current assignee: Ansaldo Energia IP UK Ltd
Priority date: 2008-02-13
Filing date: 2009-01-20
Publication date: 2011-10-06
Anticipated expiration: 2029-01-20
Also published as: EP2090830A1; US20090211257A1; US8196409B2; AU2009200205A1; EP2090830B1

Abstract

Summary The present invention concerns a fuel supply arrangement for a gas turbine burner (16), said fuel distribution arrangement comprising: a rear section (C) 5 external to the burner (16) located between a turbine wall (27) and a fuel distribution system interface (19) directing fuel into fuel supply circuits, said fuel distribution system interface (19) having four fuel connections, being for liquid fuel, gaseous fuel, pilot gas and liquid pilot fuel; an intermediate section (B) located between the turbine wall (27) and the backside wall (28) of a distribution 10 chamber (33); and a front section (A) in front of the second section located between said backside wall of the distribution chamber and a burner central backside block (29); said fuel distribution arrangement comprising a pipe (8) for gaseous fuel, a pipe (1) for liquid fuel, particularly oil, as well as a pipe (5) for pilot gas, and a pipe for liquid pilot fuel (6), particularly pilot oil. In the rear 15 section the pipe for gaseous fuel and the pipe for liquid fuel are arranged concentrically, and in at least one portion of the intermediate section the pipe for gaseous fuel is arranged non-concentrically with the liquid fuel pipe. (Fig. 2) C4m

Description

1 Gas turbine Technical field 5 This invention relates to a gas turbine comprising a fuel supply system arrangement for a premixing burner and is suited for gaseous and/or liquid fuel supply. It provides (premix) fuel and pilot fuel for combustion as well as a mounting support for the fuel lance and the bumer-swirl body inside an engine. 10 Background of the invention Premixing burners for the operation of gas turbine plants are operated with different fuel feed systems. It is a challenge to cover the entire load range of a gas turbine, i.e. from the ignition and starting phase up to the full-load range. 15 This is achieved by supplying premixing burners with pilot gas during starting and in lower load ranges, whereas after the start-up phase, premix fuel is supplied to the system in order to raise the burner capacity. A good coordination between the pilot gas supply and the premix fuel supply in connection with the simultaneous feed of different mediums therefore is aspired. 20 Burners in common combustion systems are usually provided with fuel supply systems in which the gaseous fuel pipe is conducted to the combustion chamber concentrically with the liquid fuel pipe. 25 The present invention aims to provide an improved fuel supply system for Premix-burners (as called EV-Bumer) generally of the type as for instance described in EP-A1-0 321 809, particularly for an advanced Premix 2 burner (as called AEV-bumer), generally of the type as for instance described in EP A1-0 704 657, so as to allow a facilitated assembly and maintenance, minimized pipe size and maximum flexibility of pipe conduct. The contents of the mentioned burners are incorporated into this application. 5 The fuel supply systems of the state of the art entail problems in terms of mounting and maintenance of the fuel pipes, particularly of the fuel lance used for liquid fuel piping. In addition, the pipes used to pipe the gaseous fuel have to be of a rather large diameter so as to house the fuel lance for the liquid fuel 10 concentrically within it. If one pipe needs to be exchanged, or maintenance has to be performed in either of the pipes, both the liquid fuel pipe (preferably the fuel lance) and the gaseous fuel pipes have to be disassembled. Also, due to the concentric arrangement of the liquid fuel- and the gaseous fuel pipes, thermal expansion cannot be compensated easily. 15 None of the existing fuel supply systems can solve these problems, as long as the fuel lance is conducted coaxially and concentrically within the gaseous fuel pipe, particularly within the inner of two pipes comprising the gaseous fuel pipe. 20 Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application. 25 Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, 30 integers or steps.

3 According to the present invention there is provided a fuel supply arrangement for operating a burner of a gas turbine, wherein said fuel supply arrangement comprises a rear section, an intermediate section, and a front section, wherein the rear section is located external to the 5 burner and is arranged between a turbine wall being part of the gas turbine and a fuel distribution system interface directing fuel into fuel supply circuits, wherein said fuel distribution system interface having four fuel connections, being for liquid fuel, gaseous fuel, pilot gas and liquid pilot fuel, wherein the intermediate section is located between the turbine 10 wall and a backside wall of a distribution chamber, wherein the front section is located in front of the intermediate section and is arranged between said backside wall of the distribution chamber and a burner central backside block, wherein said fuel supply arrangement comprises a gaseous fuel pipe for gaseous fuel, a liquid fuel pipe for liquid fuel, 15 particularly oil, as well as a pilot gas pipe for pilot gas, and a liquid pilot fuel pipe for liquid pilot fuel particularly pilot oil, wherein in the rear section the gaseous fuel pipe and the liquid fuel pipe are arranged concentrically, and in that in at least one portion of the intermediate section the gaseous fuel pipe is arranged non-concentrically 20 with the liquid fuel pipe. The fuel supply system arrangement is suited for example for an advanced environmental friendly v-shaped premix-bumer (AEV-bumer), or any other burner with similar interface in an engine. The AEV-bumers are capable of 25 prevaporizing and premixing liquid fuel prior to combustion. Importantly at least over a portion of the fuel supply arrangement, the gaseous fuel pipe and the liquid fuel pipe are provided as non-concentric pipes conducted parallel to each other over at least one portion of the front-and/or intermediate 30 and/or rear sections(s) of the fuel supply arrangement. In addition, the piloting tubes, i.e. the pipes for pilot gas and/or liquid pilot fuel are preferably provided as separate tubes extending over the full length of the fuel supply arrangement until the corresponding injection ports into the combustion chamber. The eccentric fuel supply allows a better cyclic life and eigenfrequency.

3A In a first preferred embodiment of the present invention, in at least one portion of the intermediate section, the gaseous fuel pipe is comprised of at least one 5 pipe outside the periphery of the wall of the liquid fuel pipe. In another preferred embodiment of the present invention, in at least one portion of the intermediate section the gaseous fuel pipe is comprised of more than 1, preferably 2, 3, 4, or 5 pipes. 10 In the rear section of a further preferred embodiment of the present invention, the gaseous fuel pipe is comprised of and/or bordered by an inner pipe and an outer pipe and that in the rear section the liquid gas pipe is arranged coaxially 4 and concentrically within said inner gaseous fuel pipe. According to another preferred embodiment of the present invention, in at least one portion of the rear section the pilot gas pipe and/or the liquid pilot fuel pipe 5 is guided within the gaseous fuel pipe. In the rear section of a further embodiment of the invention, the liquid fuel entry port is located in the fuel distribution system interface such that the liquid fuel is axially introduced into the liquid fuel pipe from the rear and that the gaseous 10 fuel entry port and/or the pilot gas entry port is located in the fuel distribution system connection block such that the gaseous fuel and/or the pilot gas is radially insertable into the gaseous fuel pipe and/or the pilot gas pipe and/or the liquid pilot fuel pipe, preferably perpendicular to the liquid fuel flow direction. 15 It is of further advantage, if in at least one portion of the rear section at least some of the fuel pipes are arranged as three concentric pipes. Preferably, the fuel lance is the innermost of the concentrically arranged pipes, followed outwardly by the inner gaseous fuel pipe and then the outer gaseous fuel pipe. Between the inner gaseous fuel pipe and the outer gaseous fuel pipe, 20 preferably the pilot fuel pipes are provided in the rear section. However, the course of the pilot fuel pipes can, in one ore more portions of the rear section, be at an angle to the longitudinal axis of the fuel supply arrangement. Between the fuel lance and the inner gaseous fuel pipe, an interspace, filled with air, preferably is provided. 25 Furthermore, it is preferred that the intermediate section the gaseous fuel pipe is provided individually from, parallel to and axially offset to the liquid fuel pipe. The gaseous fuel pipe, after leaving the burner flange, provides the continuation of the housing of the gaseous fuel pipe, which in section is provided in the 30 space between the inner gaseous fuel pipe and the outer gaseous fuel pipe.

5 According to another preferred embodiment of the present invention, between the gaseous fuel pipe in the rear section and the gaseous fuel pipe in the intermediate section, an interface is provided, said interface being disposed at 5 an angle a adapted to guide the gaseous fuel frontwardly and outwardly with respect to the longitudinal axis of the fuel supply arrangement. Said angle can be any angle of 0-90 degrees, preferably an angle of about 45 degrees. Furthermore, a fuel supply arrangement is suggested, wherein the liquid fuel 10 pipe is provided as a fuel lance extending parallel to the longitudinal axis of the fuel supply system and over all three sections thereof until an injection port of the liquid fuel at the front tip of the fuel lance into the mixing section of a burner. Thus, the fuel lance preferably doesn't change it's course while extending over the fuel supply arrangement. 15 It is advantageous if in the intermediate section the gaseous fuel pipe is provided parallel to the fuel lance. Said gaseous fuel pipe has its own longitudinal axis, which thus is preferably provided parallel to the longitudinal axis of the fuel supply system. 20 Preferably, in at least one portion of at least one of the three sections of the fuel supply system at least one fuel pipe is designed such as to compensate for thermal expansion during operation. 25 Furthermore, preferably the liquid pilot fuel pipe and/or the pilot gas pipe is arranged as a spiral or as at least one essentially circumferential portion around the fuel lance and/or another fuel pipe. A further preferred fuel supply arrangement according to the present invention 30 is provided with mounting support means for the fuel lance. The fuel supply 6 arrangement is preferably held by at least one support means in each section. In the rear section, preferably the connection block to the fuel distribution system and/or the backplate serve this support function, whereas in the intermediate section the burner flange, and in the front section the back wall of 5 the gaseous fuel plenum provide support to the fuel lance, preferably in addition to supporting other fuel pipes as well. Further embodiments of the present invention are outlined in the dependent claims. 10 Short description of the figures In the accompanying drawings preferred embodiments of the invention are shown in which: 15 Figure 1 is a schematic axial cut through a two-chamber gas turbine according to the state of the art; Figure 2 is schematic axial cut through a fuel supply arrangement according to one embodiment of the present invention; 20 Figure 3 is a perspective view of a fuel supply arrangement of figure 3, wherein, however, in the rear section C the pipes disposed within the outer gaseous fuel pipe are not shown. 25 Detailed description of the preferred embodiments Referring to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same, figure 1 shows a schematic axial cut through a gas turbine with two sequential combustion chambers. The depicted gas turbine comprises a circular 7 row of environmentally friendly v-shaped burners 16 (as called EV-burner) and of sequential self-ignition combustion chamber 18. In such a sequential combustion system, combustion air is compressed in the compressor 13 and is then guided into the first combustion chamber 17, an 5 annular combustion chamber with a circle of several EV-burners 16, where it is heated. After the injection of fuel and its mixing with the combustion air, the mixture is expanded in a first turbine/expansion stage 36 and guided into a sequential self-ignition combustion chamber 18 (as called SEV-burner), where the air is mixed with fuel again. The gas is then expanded through a second 10 turbine/expansion stage 14. Thereby, thermal energy is transformed to mechanical energy, which is partially used to drive the compressor 13, but mainly to drive a generator or the like. The depicted combustion system has, described from outside to inside, a peripheral turbine wall 27, followed by a flow space 35 for compressed air 15 located between said turbine wall 27 and a burner housing 40 around the annular combustion chamber 17 and a distribution chamber 33. From right to left in figure 1, a compressor 13 is provided "below" (with respect to the figure) a fuel supply arrangement. The fuel supply arrangement is divided into three sections A, B, C. The rear section C of the fuel supply 20 system/arrangement is located behind the turbine wall 27, and is provided with a burner flange 7, with which the fuel supply arrangement is mounted/fastened in an opening 44 of the turbine wall 27. An intermediate section B is located between said turbine wall 27 and a backside wall 28 of a distribution chamber 33 located annularly around the turbine axis A and housing the multi-cone swirl 25 generator/mixing section of the burner 16. Said fuel supply system is mounted in an opening of the backside wall 28 with a heat retaining shield 10. Therefore, the fuel supply arrangement is fastened/held, i.e. clamped/anchored at least at two points in the turbine: firstly it is mounted within opening 44 of the turbine wall 27, anchored in said opening 44 by flange 7, and secondly within an 30 opening 47 in the backside wall 28 of the distribution chamber 33.

8 The front section A is located in front of said backside wall 28 of the distribution chamber 33 and connects the fuel supply arrangement to the multi-cone burner arrangement 16 via a burner central backside block 29. Left/downstream of said backside block 29, which is designed as a pressure cast part, and downstream 5 of the burner 16, the annular combustion chamber 17 follows. The self-ignition combustion chamber 18, has optional a vortex generator/swirler 20 in order to create turbulences in the combustion air so as to allow better mixing with the fuel injected into the flow path in the second sequential combustion chamber 30. Following combustion and heating in said second sequential combustion 10 chamber 30, the gas is expanded in a second turbine stage 14. In Figure 2, a fuel supply arrangement according to one embodiment of the present invention is shown schematically. The fuel supply system shown extends from the interface 19 to the fuel distribution system (not shown) on the 15 far right in the figure to the tip of the fuel lance 31 on the far left and comprises, with respect to the longitudinal axis L of the fuel supply arrangement the three sections A, B, C mentioned above. Section C is limited on the far right by a introduction element 45, which comprises a connecting block 2 and a back plate, surrounded by an interface 19 to the main fuel distribution system (not 20 shown), indicated by a dotted line in figure 2. Said introduction element 45 houses the fuel entry ports (, 24, 25, 39). Section C is divided from section B by burner flange 7, which anchors the fuel supply system in the opening 44 of the turbine wall 27 (shown in figure 1) and also has a shielding function. In figure 2, a dotted line indicates the connection point for the turbine wall 27. Furthermore, 25 section B is divided from section A by a pot-like element, which is fastened to the backside block 28 of the distribution chamber 33 (air plenum, shown in figure 1) over a heat retaining shield 10, which is supported by a flange 9. Coming from the rear end of the fuel supply arrangement, i.e. the main fuel distribution system (not shown), from the rear section C over the intermediate 30 section B to the front section A, various fuel pipes 5, 6, 8, and fuel lance 31 extend across these dividing elements 45, 7, (core elements of the fuel supply arrangement) to the front end of the fuel supply arrangement. According to 9 figure 2, the rear section C is connected on the right side to an interface to the main fuel distribution system (not shown) with a connection block 2. Said block 2 comprises toward the rear a backplate 15. The fuel disposed within the interface 19 surrounds the connection block 2 and the backplate 15 before 5 entering into the fuel entry ports 23, 24, 25, 39. Both the connection block 2 and the backplate 15 are summarized for explanation purposes as introduction element 45. Said introduction element 45 has four fuel connections, i.e. a liquid fuel entry port 39, a gaseous fuel entry port 24, a pilot gas entry port 25 and liquid pilot fuel entry port 23 (shown in figure 3), and directs the fuel into the 10 corresponding fuel supply circuits 1, 5, 6, 8. The entry port 24 for the gaseous fuel as well as the entry port 25 for the pilot gas are arranged such that the fuel is introduced radially into their respective pipes 5, 8, at an angle perpendicular to the main longitudinal axis L of the fuel supply arrangement. The entry port 23 (see figure 3) for the liquid pilot fuel into the liquid pilot fuel pipe 6 is not shown 15 in figure 2 as the entry port is arranged perpendicularly to the other two entrance ports 24, 25. It is possible to arrange the fuel entry ports at other angles as well. Liquid fuel is supplied into the combustion chamber through a fuel lance 31. An entrance port 39 for the liquid fuel is provided such that the liquid fuel is injected into the liquid fuel pipe in an axial direction with respect to 20 the longitudinal axis L of the fuel supply system. In said rear section C, four fuel pipes are thus present: The liquid fuel pipe 1, preferably for oil, which continues in a straight design axially over all three sections A, B, C along and axial with the longitudinal axis L of the fuel supply arrangement; furthermore pipe 8 for the gaseous fuel, which in the rear section C passes between an inner pipe 4, with 25 an interspace 26, and an outer pipe 3; Said pipe 1 for the liquid fuel is provided in figure 2 as the fuel lance 31, extending coaxially and concentrically with the gaseous fuel pipe 8 and its pipes 3, 4 respectively in section C. Therefore, the liquid fuel pipe 1 and the gaseous fuel pipe 8 are arranged as three concentric pipes 3, 4, 31 in the rear section C; furthermore a pipe 5 for pilot gas is located 30 radially outside of the liquid fuel pipe 1 and within the gaseous fuel pipe 8 over a large portion of the rear section C; and, also radially outside of the liquid fuel pipe 1 and within the gaseous fuel pipe 8, a liquid pilot fuel pipe 6 is provided, guided in the liquid pilot fuel pipe according to figure 2. According to figure 2, in 10 section C, the pilot gas pipe 5 and the liquid pilot fuel pipe 6 are separate pipes, both located in the interspace 32 between the walls of the inner pipe 4 and the outer pipe 3, thus within the gaseous fuel pipe 8. Coming from the rear, i.e. the right side in figure 2, pipe 5 for the pilot gas changes its initial direction before 5 reaching the burner flange 7, the corresponding pilot gas pipe 5 describing a partially circumferential section for the purpose of compensating for thermal expansion, before continuing in an axially offset direction in section B. Said compensation effect is due to the elastic property that a pipe section gains in axial direction when it is arranged circumferentially with respect to the 10 longitudinal axis L of the arrangement instead of axially. In effect, preferably each pilot fuel pipe 5, 6 contains at least one at least partial circumferential section in at least one, preferably each of the sections A, B, C of the fuel supply arrangement. In the upstream area, i.e. the rear section C, the gaseous fuel pipe 8 is made from two concentric pipes 3, 4. The connection block 2 to the 15 fuel distribution system and the burner flange 7 are preferably welded to said pipes 3, 4. Between sections C and B, within the burner flange 7, an interface 32 is provided, where the circumferential gaseous fuel pipe 8 merges into a single pipe. Before entering said interface 32, the gaseous fuel is piped from the circumferential pipe 8 made from concentric pipes 3 and 4, into a conical area 20 within the flange 7 and then diverged into said interface 32. The interface 32 has an axis W, which is at an angle with respect to the main longitudinal axis L of the fuel supply arrangement at an angle a. In figure 2, said angle a is about 45 degrees, however, other angles between 0 and 90 degrees is possible. The angled arrangement of the interface 32 allows a low flow resistance. 25 The gaseous fuel pipe 8 continues non-concentrically with the liquid fuel pipe 1, i.e. the fuel lance 31, throughout the entire length of the intermediate section B along the longitudinal axis L. Thus, in the intermediate section B, the gaseous fuel flows through a gaseous fuel pipe 8a parallel to the longitudinal axis L, 30 traverses the pot-like element which marks the transition between section B and section A. In the intermediate section B, four fuel pipes are present in parallel 11 arrangement. In figure 3, over the entire intermediate section B, the gaseous fuel pipe 8 is provided as a pipe, with a longitudinal axis M radially offset outwardly from the other three pipes 1, 5, 6, parallel to the longitudinal axis L of the fuel supply arrangement. Below the gaseous fuel pipe 8, the liquid fuel pipe 5 1 in form of the fuel lance 31 is located parallel to and "below" of said gaseous fuel pipe 8a. Said separate conduct of the four fuel pipes in separate fuel pipes 5, 6, 8, 31 continues through the entrance to the distribution chamber 33 (air plenum, shown in figure 1) or through its backside wall 28, respectively, where a heat retaining shield 10 is supported on support 9. 10 After passing through the cavity of the pot-like element, which is preferably filled with air, the gaseous fuel pipe 8a merges into a gaseous fuel plenum 11, with a back wall 11 a located at the far left in the figure in the front section A. Thereby, when leaving the gaseous fuel pipe 8, the gaseous fuel enters into a circumferential pipe again in section A, embodied by the gaseous fuel plenum 15 11. Interior of the heat retaining shield 10, the liquid pilot fuel pipe 6a is spiraled about the fuel lance 31. This spiral arrangement can also be located in any of the three sections A, B, C. It has the purpose to compensate for the thermal expansion. Such compensation means can be introduced into the system by 20 such a spiral arrangement or any other pipe arrangement known to allow thermal tolerances. As described before, the pilot gas pipe 5 as well as the liquid pilot fuel pipe 6 can be provided with a "partially spiraled" (6a) / partially circumferential section, in any, preferably at least one, preferably in each of the three sections A, B, C. 25 Each fuel pipe can be provided in several portions, which can be welded together and coupled to the different dividing elements such as for example the introducing element 45, the burner flange 7, or the pot-like element, e. g. by a coupling element 38. 30 An extension tube 12, an interspace 46 is provided, which is filled with air, of the 12 gaseous fuel inner pipe 4 surrounds the fuel lance 31 in a concentric arrangement in the gaseous fuel plenum 11 continuing downstream from a pot like element. Therefore, in the front section A, the pipes 5, 6 for liquid pilot fuel and pilot gas are still located separately from and non-concentrically with the 5 liquid fuel pipe 1 and/or the gaseous fuel pipe 8. However, the gaseous fuel pipe 8 and the liquid fuel pipe 1 are again arranged concentrically within at least one portion of this front section A. The tip 34 of the fuel lance 31, which is provided with openings for the injection of liquid fuel into the combustion air stream, is located downstream of the interface 29 to the burner-swirler with 10 respect to the liquid fuel flow direction F, extending through burner central backside block 29 into the tip of the burner cone. As mentioned above, the gaseous fuel pipe 8 is guided into a gaseous fuel plenum 11 after passing the heat retaining shield 10. In the area of the gaseous 15 fuel plenum 11, the gaseous fuel is again piped concentrically with the liquid fuel pipe 1, the extension tube 12 and the gaseous fuel plenum 11 surrounding the fuel lance 31 concentrically. The plenum in the front section C has a diameter greater than the diameter of the gaseous fuel pipe in the intermediate section B and preferably also greater than the annular gaseous fuel pipe 8 20 comprised of the concentric inner and outer gaseous fuel pipes 3 and 4 in the rear section C. Preferably, the gaseous fuel plenum 11 is designed with tapered walls, wherein the diameter of the plenum at the gaseous fuel injection port is smaller than the diameter of the plenum at its interface to the front end of the gaseous fuel pipe 8. 25 Thus, as the liquid fuel pipe 1 extends partially into the burner cone, and the gaseous fuel is injected from annularly disposed openings in the plenum 11 at the interface 29 to the burner-swirl body, the liquid fuel is injected into the burner further upstream than the gaseous fuel with respect to the liquid fuel flow 30 direction F.

13 Preferably, at the interface 29 to the burner-swirler, the parts of the fuel supply system are welded to parts of the annular burner arrangement. Preferably, the burner-swirler), the extension tube 12 and the gaseous fuel plenum 11 are welded together. 5 For the purpose of pilot fuel injection, at least one pipe 5, 6 is provided via connections 21, 22 to supply liquid pilot fuel and/or pilot gas fuel from the end of the burner 16 to the fuel injection port, designed as a liquid pilot fuel injection nozzle and a pilot gas plenum (not shown). At connections 21 and 22, the pilot 10 gas pipe 5a and the liquid pilot fuel pipe 6a are coupled to their injection ports even further downstream than the liquid fuel into the burner 16 (shown in figure 1), preferably formed as a cone. Figure 2 shows pilot pipes 5 and 6 located radially offset with respect to the liquid fuel pipe 1. The liquid pilot fuel pipe 6a extends to a connection 21 to its injection port within the combustion chamber 15 17 (shown in figure 1). The liquid pilot fuel- and pilot gas pipes 5, 6 are not drawn in their full length in figure 2. In effect, the injection ports for liquid pilot fuel and pilot gas, respectively, are connected to the pipes by connections 21, 22, which can be made integrally with the pipe(s) and the injection port(s), and are located further downstream than the connections 21, 22 depicted in the 20 figure. The ends 42, 43 of said pipes 5, and 6, respectively can be seen in figure 3. Figure 3 shows the fuel supply arrangement of figures 2, however, in section C, the pipes disposed within the outer gaseous fuel pipe 3, which are the fuel lance 25 31, the pilot gas pipe 5a and the liquid pilot fuel pipe 6a, as well as the inner gaseous fuel pipe 4, are not shown. Said pipes exit the burner flange in the intermediate section B, which is provided with a flow space 35 of combustion air, as fuel lance 31, pilot gas pipe 5a and liquid pilot fuel pipe 6a, as well as gaseous fuel pipe 8a (continuation of inner and outer gaseous fuel pipes 3, 4) 30 and are visible from then on again. In figure 3, the circumferential portion of the liquid pilot fuel pipe 6 in the front section A is better visible than in figure2.

14 List of reference numerals 1 Liquid fuel pipe 2 Connection block to fuel distribution system 5 3 Gaseous fuel outer pipe 4 Gaseous fuel inner pipe 5 Pilot gas pipe 6 Liquid pilot fuel pipe 6a Spiraled pipe 10 7 Burner flange 8 Gaseous fuel pipe 9 Support for heat retaining shield 10 Heat retaining shield 11 Gaseous fuel plenum 15 11a Back wall of 11 12 Extension tube 13 Compressor 14 Second expansion phase, turbine 15 Back plate 20 16 Premix-burner, multi-cone burner arrangement 17 First annular combustion chamber 18 Self-ignition combustion chamber 19 Interface to fuel distribution system 20 Vortex generator 25 21 Connection to liquid pilot fuel injection port 22 Connection to pilot gas injection port 15 23 Liquid pilot fuel entry port in 2 24 Gaseous fuel entry port in 2 25 Pilot gas entry port in 2 26 Inter space 5 27 Turbine wall 28 Backside wall of 33 29 Burner central backside block, interface to burner-swirler, pressure cast part 30 Second sequential combustion chamber 10 31 Fuel lance 32 Interface between 3, 4 and 8a, i.e. between 8 in C and 8 in B 33 Distribution chamber 34 Combustion chamber backside wall 35 Flow space of compressed air 15 36 First expansion phase, turbine 37 Turbine housing 38 Coupling element 39 Liquid fuel entry port 40 Burner housing 20 42 Liquid pilot fuel injection port 43 Pilot gas fuel injection port 44 Opening in 27 45 Introduction element comprising 2 and 15 46 Inter space between 12 and 31 25 47 Opening in 28 A Front section between 28 and 29, first section 16 a Angle between L and W B Intermediate section between 27 and 28, second section C External rear section behind 27, third section F Liquid fuel flow direction 5 L Longitudinal axis of fuel supply system M Axis of 8 in B T Longitudinal axis of gas turbine W Longitudinal axis of 32 10

Claims

1. A fuel supply arrangement for operating a burner of a gas turbine, wherein said fuel supply arrangement comprises a rear section, an intermediate section, and a front section, wherein the rear section is 5 located external to the burner and is arranged between a turbine wall being part of the gas turbine and a fuel distribution system interface directing fuel into fuel supply circuits, wherein said fuel distribution system interface having four fuel connections, being for liquid fuel, gaseous fuel, pilot gas and liquid pilot fuel, wherein the intermediate 10 section is located between the turbine wall and a backside wall of a distribution chamber, wherein the front section is located in front of the intermediate section and is arranged between said backside wall of the distribution chamber and a burner central backside block, wherein said fuel supply arrangement comprises a gaseous fuel pipe 15 for gaseous fuel, a liquid fuel pipe for liquid fuel, particularly oil, as well as a pilot gas pipe for pilot gas, and a liquid pilot fuel pipe for liquid pilot fuel particularly pilot oil, wherein in the rear section the gaseous fuel pipe and the liquid fuel pipe are arranged concentrically, and in that in at least one portion of 20 the intermediate section the gaseous fuel pipe is arranged non concentrically with the liquid fuel pipe.

2. The fuel supply arrangement of claim 1, wherein in at least one portion of the intermediate section the gaseous fuel pipe is comprised of at least one pipe outside the periphery of the wall of the liquid fuel pipe. 25

3. The fuel supply arrangement of claim 2, wherein the at least one portion of the intermediate section the gaseous fuel pipe is comprised of more than 1, preferably 2, 3, 4, or 5 pipes. 30

4. The fuel supply arrangement according to one of claims 1 to 3, wherein in the rear section the gaseous fuel pipe is comprised of and/or bordered by an inner pipe and an outer pipe and that in the rear section (C) the liquid gas pipe is arranged coaxially and concentrically within said inner gaseous fuel pipe.

5 5. The fuel supply arrangement according to one of the preceding claims, wherein in at least one portion of the rear section the pilot gas pipe and/or the liquid pilot fuel pipe is guided within the gaseous fuel pipe. 10

6. The fuel supply arrangement according to one of the preceding claims, wherein in the rear section (C) the a liquid fuel entry port is located in the fuel distribution system interface such that the liquid fuel is axially introduced into the liquid fuel pipe from the rear and that the gaseous fuel entry port and/or the pilot gas entry port is located 15 in the fuel distribution system connection block such that the gaseous fuel and/or the pilot gas is radially introduceable into the gaseous fuel pipe and/or the pilot gas pipe and/or the liquid pilot fuel pipe, preferably perpendicular to the liquid fuel flow direction (F). 20

7. The fuel supply arrangement according to one of the preceding claims, wherein in at least one portion of the rear section (C) at least some of the fuel pipes are arranged as three concentric pipes.

8. The fuel supply arrangement according to one of the preceding 25 claims, wherein in the intermediate section (B) the gaseous fuel pipe is provided individually from, parallel to and axially offset to the liquid fuel pipe.

9. The fuel supply arrangement according to one of the preceding 30 claims, wherein between the gaseous fuel pipe in the rear section (C) and the gaseous fuel pipe in the intermediate section (B), an interface is provided, said interface being disposed at an angle (a) adapted to guide the gaseous fuel frontwardly and outwardly with respect to the longitudinal axis (L) of the fuel supply arrangement.

10. The fuel supply arrangement according to one of the preceding claims, wherein the liquid fuel pipe is provided as a fuel lance extending parallel to the longitudinal axis (L) of the fuel supply system and over all three sections (A, B, C) thereof until an injection port of the liquid fuel at the a front tip of the fuel lance into the mixing section of a burner.

11. The fuel supply arrangement according to one of the preceding claims, wherein in the intermediate section (B) the gaseous fuel pipe is provided parallel to the fuel lance.

12. The fuel supply arrangement according to one of the preceding claims, wherein in at least one portion of at least one of the three sections (A, B, C) of the fuel supply system at least one fuel pipe is designed such as to compensate for thermal expansion during operation.

13. The fuel supply arrangement according to claim 11, wherein the liquid pilot fuel pipe and/or the pilot gas pipe is arranged as a spiral or as at least one essentially circumferential portion around the fuel lance and/or another fuel pipe.

14. The fuel supply arrangement according to one of the preceding claims, wherein mounting support means for the fuel lance are provided.

15. A fuel supply arrangement substantially as hereinbefore described with reference to Figures 2 and 3 of the drawings.